SAT Question aa2d36fe: Circles answer and explanation with Desmos solution

Choice A is correct. For a circle in the xy-plane that has the equation ${\left(x-h\right)}^2+{\left(y-k\right)}^2=r^2$, where $h$, $k$, and $r$ are constants, $\left(h,k\right)$ is the center of the circle and the positive value of $r$ is the radius of the circle. In the given equation, $h=13$ and $r^2=64$. Taking the square root of each side of $r^2=64$ yields $r=\pm 8$. Therefore, the center of the circle is at $\left(13,k\right)$ and the radius is $8$.